CHEMISTRY FORM 2
- 1.1 Structure of the atom
- 1.2 Atomic Number and Mass Number
- 1.3 Isotopes
- 1.4 Energy levels and electron arrangement
- 1.5 Development of the Periodic Table
- 1.6 Relative Atomic Mass and Isotopes
- 1.7 Ion Formation
- 1.8 Chemical Formulae
- 1.9 Chemical Equations
- 2.1 Alkali metals (Group I elements)
- 2.2 Alkali Earth Metals (Group II elements)
- 2.3 Halogens (Group VII elements)
- 2.4 Noble gases (Group VIII elements)
- 2.5 Properties and Trends Across the Periodic Table
- 3.1 Bond
- 3.2 Ionic bond
- 3.3 Giant ionic structure
- 3.4 Covalent bond
- 3.5 Co-ordinate bond
- 3.6 Molecular structures
- 3.7 Giant covalent structures
- 3.8 Metallic Bond
- 3.9 Types of bond across a period
- 3.10 Oxides of elements in Period 3
- 3.11 Chlorides of Period 3 elements
- 4.1 What is a salt?
- 4.2 Types of salt
- 4.3 Solubility of salts in water
- 4.4 Methods of preparing salts
- 4.4.1 Reacting a Metal with an Acid
- 4.4.2 Reacting an Acid with a Base (Neutralization)
- 4.4.3 Reacting an Acid with a Carbonate (or hydrogencarbonate of metal)
- 4.4.4 Combining elements Directly (Direct Combination of elements)
- 4.4.5 Precipitation (Double decomposition)
- 4.5 Action of heat on salts
- 4.6 Uses of salts
- 5.1 Electrical conduction
- 5.2 Electrical conductivity of molten substances
- 5.3 Electrical conductivity of substances in aqueous state
- 5.4 Electrolysis
- 5.5 Applications of electrolysis
- 6.1 Allotropes of carbon
- 6.2 Chemical properties of carbon
- 6.3 Carbon (IV) oxide
- 6.4 Carbon (II) oxide (CO)
- 6.5 Large scale production of sodium carbonate and sodium hydrogencarbonate
- 6.6 Effect of carbon (II) oxide and carbon (IV) oxide on the environment
- 6.7 Carbon cycle
Chemical Bonding and Structure: Co-ordinate bond
3.0 Chemical Bonding and Structure
3.5 Co-ordinate bond
Earlier, we met ammonium ion (NH4+) and carbon (II) oxide (CO). How do the formulae come about?
Consider the structure of ammonia drawn earlier. In the presence of an acid, which has hydrogen ions (H+), the unshared electron pair (xx) on ammonia is readily shared with the ion, because the latter has an empty energy level. The product is ammonium ion (NH4+). See Figure 3.5(a).
Figure 3.5(a): Co-ordinate bond in ammonium ion
In this case, the shared electron pair comes from the same atom, nitrogen. A bond so formed is called a co-ordinate (or dative) bond. Co-ordinate bond is one in which the shared pair of electrons comes from the same atom. An arrow is normally used to distinguish co-ordinate bond from covalent bond, because they both involve electron sharing.
Co-ordinate bond also occurs in carbon (II) oxide (Figure 3.5(b)).
Figure 3.5(b): Coordinate bond in carbon(II)oxide
Questions 3.5
- Water (H2O) also forms co-ordinate bond with hydrogen ion (H+). Specifically, H+ bonds with the oxygen atom in water. Draw a diagram similar to Figure 3.5(a) to show the bonding.
- Distinguish between co-ordinate bond and covalent bond.
Answers to Questions 3.5
The product formed when water combines with hydrogen ion is called oxonium ion (H3O+). This is the form in which hydrogen ions actually exist in solutions.
Co-ordinate and covalent bonds are similar in many aspects. They occur between non-metals, and involve sharing of electrons. The difference is that in co-ordinate bonds, the shared pair of electrons comes from the same atom.